The present invention relates to a graphics processing system and, more particularly, to a graphics processing system adapted to improve the quality of display on a screen by appropriately deleting a line image in a segment in which the line image is displayed under or overlaps with graphics produced on the basis of vector data.
Heretofore, a graphics processing system as a computer-aided design (CAD) system or the like forms graphics data of vector data from an original image data of a line image of a drawing inputted from an image input device such as an image scanner. In this case, the original image data of a line image is displayed on the display screen of a display device so as to overlap with the graphics data of the vector data, and the graphics data is formed by inputting a line connecting one terminal point (start point) to another terminal point (end point) of the graphics data on the display screen by means of a pointing device such as a mouse from the state of a line, such as a line width, a line length and a line shape of the line image and consequently by forming line vector data. And, the line image to be disposed under the line vector data inputted is processed so as to be deleted on the display screen in order to permit an easy look at the display screen.
In such a graphics processing system, however, the processing of deleting the line image in a segment in which the line image is disposed under or overlap with the display image of the graphics data may be implemented, for example, by setting a constant line width of the pixels of a graphics locus obtainable by an experience value in an orthogonal direction as the object for deletion and deleting the line image within the range of the line width thereof. Therefore, there is the risk that a portion of the line image which is not the object for deletion and which is located in the vicinity of the line image as the object for deletion is to be deleted and that a portion of the line image as the object for deletion, which protrudes from the region of the object for deletion, can be left undeleted.
In the delete processing for the line image displayed under the display image of the graphics data, the range for deletion specified by a line width of the line image is set constant so that a portion of the pixels constituting the line image, which is located outside the range for deletion, is left undeleted or a portion of the pixels which constitutes the line image as the object not to be deleted yet which is located adjacent and within the range for deletion, is deleted. Hence, conventional delete processing allows a portion of the line image to be undeleted or deleted excessively, thereby decreasing the quality of display of a display screen.